diff --git a/php/src/php/types/_schema.php b/php/src/php/types/_schema.php
new file mode 100644
index 0000000..e0cc6e9
--- /dev/null
+++ b/php/src/php/types/_schema.php
@@ -0,0 +1,58 @@
+<?php
+namespace nulib\php\types;
+
+use nulib\exceptions;
+use nulib\str;
+
+class _schema {
+  /** @var array association type simple / vclass */
+  const VCLASSES = [
+    "rawstring" => vrawstring::class,
+    "string" => vstring::class,
+    "text" => vtext::class,
+    "bool" => vbool::class,
+    "int" => vint::class,
+    "float" => vfloat::class,
+    "array" => varray::class,
+    "func" => vfunc::class,
+    "raw" => vraw::class,
+    "mixed" => vmixed::class,
+    "key" => vkey::class,
+    "pkey" => vpkey::class,
+    "content" => vcontent::class,
+    "datetime" => vdatetime::class,
+    "date" => vdate::class,
+    "time" => vtime::class,
+  ];
+
+  static function get_types($schema, &$default = null, ?bool &$required = null): array {
+    if (is_array($schema)) {
+      $types = $schema["type"] ?? $schema[0] ?? null;
+      $default = $schema["default"] ?? $schema[1] ?? null;
+      $required = vbool::with($schema["required"] ?? false);
+    } elseif (is_string($schema)) {
+      $types = $schema;
+      $default = null;
+      $required = false;
+    } else {
+      throw exceptions::invalid_value($schema, "schema");
+    }
+    if (is_string($types)) {
+      $types = explode(",", $types);
+    } elseif (!is_array($types)) {
+      throw exceptions::invalid_value($types, "types");
+    }
+    return $types;
+  }
+
+  static function get_vclass(array $types, ?bool &$nullable): ?string {
+    foreach ($types as $type) {
+      $vclass = self::VCLASSES[$type] ?? null;
+      if ($vclass !== null) {
+        $nullable = str::del_prefix($type, "?");
+        return $vclass;
+      }
+    }
+    return null;
+  }
+}
diff --git a/php/src/php/types/assoc.php b/php/src/php/types/assoc.php
new file mode 100644
index 0000000..5380296
--- /dev/null
+++ b/php/src/php/types/assoc.php
@@ -0,0 +1,75 @@
+<?php
+namespace nulib\php\types;
+
+use nulib\exceptions;
+
+/**
+ * Class assoc: gestion simplifiée de schémas associatifs
+ *
+ * seuls les types simples sont reconnus
+ */
+class assoc {
+  /** indiquer si $array est conforme au schéma */
+  public static function check_schema(?array $array, array $schema, bool $strict = false): bool {
+    foreach ($schema as $key => $kschema) {
+      $types = _schema::get_types($kschema, $default, $required);
+      $exists = array_key_exists($key, $array);
+      if (!$exists) {
+        if ($required) return false;
+        else continue;
+      }
+      $vclass = _schema::get_vclass($types, $nullable);
+      # le test échoue si le type n'est pas supporté
+      if ($vclass === null) return false;
+      $value = $array[$key];
+      if ($value === null) {
+        if (!$nullable) return false;
+      } else {
+        if (!$vclass::isa($value, $strict)) return false;
+      }
+    }
+    return true;
+  }
+
+  /**
+   * s'assurer que $array est conforme au schéma
+   * - les clés ne sont pas créées si elles n'existent pas, sauf si la valeur
+   * est requise ou si une valeur par défaut non nulle est fournie
+   */
+  public static function ensure_schema(&$array, array $schema): bool {
+    $ensured = true;
+    foreach ($schema as $key => $kschema) {
+      $types = _schema::get_types($kschema, $default, $required);
+
+      $exists = array_key_exists($key, $array);
+      if (!$exists) {
+        if ($required) {
+          if ($default !== null) {
+            $array[$key] = $default;
+          } else {
+            throw exceptions::missing_value(null, "array", "$key est obligatoire");
+          }
+        } elseif ($default !== null) {
+          $array[$key] = $default;
+        }
+        continue;
+      }
+
+      $vclass = _schema::get_vclass($types, $nullable);
+      # le test échoue si le type n'est pas supporté
+      if ($vclass === null) {
+        $ensured = false;
+        continue;
+      }
+
+      $value = $array[$key];
+      if ($nullable) {
+        $array[$key] = $vclass::withn($value);
+      } else {
+        if ($value === null) $value = $default;
+        $array[$key] = $vclass::with($value);
+      }
+    }
+    return $ensured;
+  }
+}
diff --git a/php/src/php/types/scalar.php b/php/src/php/types/scalar.php
new file mode 100644
index 0000000..0a34b5b
--- /dev/null
+++ b/php/src/php/types/scalar.php
@@ -0,0 +1,34 @@
+<?php
+namespace nulib\php\types;
+
+use nulib\exceptions;
+use nulib\str;
+
+/**
+ * Class scalar: gestion simplifiée de schémas de valeurs simples
+ */
+class scalar {
+  /** indiquer si $value est conforme au schéma */
+  static function check_schema($value, $schema, bool $strict=false): bool {
+    $types = _schema::get_types($schema);
+    $vclass = _schema::get_vclass($types, $nullable);
+    # le test échoue si le type n'est pas supporté
+    if ($vclass === null) return false;
+    if ($value === null) return $nullable;
+    return $vclass::isa($value, $strict);
+  }
+
+  static function ensure_schema(&$value, $schema): bool {
+    $types = _schema::get_types($schema, $default);
+    $vclass = _schema::get_vclass($types, $nullable);
+    # la conversion échoue si le type n'est pas supporté
+    if ($vclass === null) return false;
+    if ($nullable) {
+      $value = $vclass::withn($value);
+    } else {
+      if ($value === null) $value = $default;
+      $value = $vclass::with($value);
+    }
+    return true;
+  }
+}
diff --git a/php/src/php/types/varray.php b/php/src/php/types/varray.php
index 210590f..e3dec00 100644
--- a/php/src/php/types/varray.php
+++ b/php/src/php/types/varray.php
@@ -2,6 +2,7 @@
 namespace nulib\php\types;
 
 use nulib\cl;
+use nulib\exceptions;
 
 class varray {
   static function isa($value, bool $strict=false) : bool {
@@ -10,7 +11,10 @@ class varray {
   }
 
   static function ensure(&$array): void {
-    if (!is_array($array)) $array = cl::with($array);
+    if (is_array($array)) return;
+    if ($array === null || $array === false) $array = [];
+    elseif (is_scalar($array)) $array = cl::with($array);
+    else throw exceptions::invalid_value($array, "array");
   }
 
   static function ensuren(&$array): void {
diff --git a/php/src/php/types/vbool.php b/php/src/php/types/vbool.php
index 3787fef..5610daa 100644
--- a/php/src/php/types/vbool.php
+++ b/php/src/php/types/vbool.php
@@ -1,6 +1,8 @@
 <?php
 namespace nulib\php\types;
 
+use nulib\exceptions;
+
 class vbool {
   /** liste de valeurs chaines à considérer comme 'OUI' */
   public const YES_VALUES = [
@@ -37,11 +39,18 @@ class vbool {
   }
 
   static function ensure(&$bool): void {
-    if (is_string($bool)) {
+    if (is_bool($bool)) return;
+    if ($bool === null) {
+      $bool = false;
+    } elseif (is_string($bool)) {
       if (self::is_yes($bool)) $bool = true;
       elseif (self::is_no($bool)) $bool = false;
+      else throw exceptions::invalid_value($bool, "boolean");
+    } elseif (is_scalar($bool)) {
+      $bool = boolval($bool);
+    } else {
+      throw exceptions::invalid_value($bool, "boolean");
     }
-    if (!is_bool($bool)) $bool = boolval($bool);
   }
 
   static function ensuren(&$bool): void {
diff --git a/php/src/php/types/vcontent.php b/php/src/php/types/vcontent.php
index 8596979..1a0aa0b 100644
--- a/php/src/php/types/vcontent.php
+++ b/php/src/php/types/vcontent.php
@@ -1,15 +1,28 @@
 <?php
 namespace nulib\php\types;
 
+use nulib\exceptions;
+use nulib\php\content\IContent;
+use nulib\php\content\IPrintable;
+
 class vcontent {
   static function isa($value, bool $strict=false) : bool {
     if ($strict) return is_array($value) || is_string($value);
-    else return is_array($value) || is_scalar($value);
+    return is_array($value) || is_scalar($value) ||
+      $value instanceof IContent || $value instanceof IPrintable;
   }
 
   static function ensure(&$content): void {
-    if ($content === null || $content === false) $content = [];
-    elseif (!is_string($content) && !is_array($content)) $content = strval($content);
+    if (is_array($content) || is_string($content)) return;
+    if ($content === null || $content === false) {
+      $content = [];
+    } elseif (is_scalar($content)) {
+      $content = [$content];
+    } elseif ($content instanceof IContent || $content instanceof IPrintable) {
+      $content = [$content];
+    } else {
+      throw exceptions::invalid_value($content, "content");
+    }
   }
 
   static function ensuren(&$content): void {
diff --git a/php/src/php/types/vfloat.php b/php/src/php/types/vfloat.php
index 13d5c7c..31e783f 100644
--- a/php/src/php/types/vfloat.php
+++ b/php/src/php/types/vfloat.php
@@ -1,6 +1,8 @@
 <?php
 namespace nulib\php\types;
 
+use nulib\exceptions;
+
 class vfloat {
   static function isa($value, bool $strict=false) : bool {
     if ($strict) return is_float($value);
@@ -8,7 +10,10 @@ class vfloat {
   }
 
   static function ensure(&$float): void {
-    if (!is_float($float)) $float = floatval($float);
+    if (is_float($float)) return;
+    if ($float === null || $float === false) $float = 0.0;
+    elseif (is_numeric($float)) $float = floatval($float);
+    else throw exceptions::invalid_value($float, "float");
   }
 
   static function ensuren(&$float): void {
diff --git a/php/src/php/types/vint.php b/php/src/php/types/vint.php
index 74e8b6a..368f3bf 100644
--- a/php/src/php/types/vint.php
+++ b/php/src/php/types/vint.php
@@ -1,6 +1,8 @@
 <?php
 namespace nulib\php\types;
 
+use nulib\exceptions;
+
 class vint {
   static function isa($value, bool $strict=false) : bool {
     if ($strict) return is_int($value);
@@ -8,7 +10,10 @@ class vint {
   }
 
   static function ensure(&$int): void {
-    if (!is_int($int)) $int = intval($int);
+    if (is_int($int)) return;
+    if ($int === null || $int === false) $int = 0.0;
+    elseif (is_numeric($int)) $int = intval($int);
+    else throw exceptions::invalid_value($int, "int");
   }
 
   static function ensuren(&$int): void {
diff --git a/php/src/php/types/vkey.php b/php/src/php/types/vkey.php
index 0769bfb..f6ef4f3 100644
--- a/php/src/php/types/vkey.php
+++ b/php/src/php/types/vkey.php
@@ -1,6 +1,8 @@
 <?php
 namespace nulib\php\types;
 
+use nulib\exceptions;
+
 class vkey {
   static function isa($value, bool $strict=false) : bool {
     if ($strict) return is_int($value) || is_string($value);
@@ -8,9 +10,11 @@ class vkey {
   }
 
   static function ensure(&$key): void {
+    if (is_int($key) || is_string($key)) return;
     if ($key === null) $key = "";
     elseif ($key === false) $key = 0;
-    elseif (!is_string($key) && !is_int($key)) $key = strval($key);
+    elseif (is_scalar($key)) $key = strval($key);
+    else throw exceptions::invalid_value($key, "key");
   }
 
   static function ensuren(&$key): void {
diff --git a/php/src/php/types/vpkey.php b/php/src/php/types/vpkey.php
index 27c8ef6..34b5036 100644
--- a/php/src/php/types/vpkey.php
+++ b/php/src/php/types/vpkey.php
@@ -1,6 +1,8 @@
 <?php
 namespace nulib\php\types;
 
+use nulib\exceptions;
+
 class vpkey {
   static function isa($value, bool $strict=false) : bool {
     if ($strict) return is_array($value) || is_int($value) || is_string($value);
@@ -8,15 +10,19 @@ class vpkey {
   }
 
   static function ensure(&$pkey): void {
-    if ($pkey === null) $pkey = "";
-    elseif ($pkey === false) $pkey = 0;
-    elseif (!is_string($pkey) && !is_int($pkey) && !is_array($pkey)) $pkey = strval($pkey);
     if (is_array($pkey)) {
       foreach ($pkey as &$key) {
         vkey::ensure($key);
       };
       unset($key);
+      return;
+    } elseif (is_int($pkey) || is_string($pkey)) {
+      return;
     }
+    if ($pkey === null) $pkey = "";
+    elseif ($pkey === false) $pkey = 0;
+    elseif (is_scalar($pkey)) $pkey = strval($pkey);
+    else throw exceptions::invalid_value($pkey, "pkey");
   }
 
   static function ensuren(&$pkey): void {
diff --git a/php/src/php/types/vrawstring.php b/php/src/php/types/vrawstring.php
index 28f1ff8..882eb61 100644
--- a/php/src/php/types/vrawstring.php
+++ b/php/src/php/types/vrawstring.php
@@ -1,6 +1,7 @@
 <?php
 namespace nulib\php\types;
 
+use nulib\exceptions;
 use nulib\str;
 
 class vrawstring {
@@ -15,7 +16,13 @@ class vrawstring {
   }
 
   static function ensure(&$string): void {
-    if (!is_string($string)) $string = strval($string);
+    if (!is_string($string)) {
+      if (is_scalar($string)) {
+        $string = strval($string);
+      } else {
+        throw exceptions::invalid_value($string, "string");
+      }
+    }
     if (static::TRIM) $string = trim($string);
     if (static::NORM_NL) $string = str::norm_nl($string);
   }
diff --git a/php/tests/php/types/assocTest.php b/php/tests/php/types/assocTest.php
new file mode 100644
index 0000000..bd40a9e
--- /dev/null
+++ b/php/tests/php/types/assocTest.php
@@ -0,0 +1,88 @@
+<?php
+namespace nulib\php\types;
+
+use nulib\tests\TestCase;
+use nulib\ValueException;
+
+class assocTest extends TestCase {
+  static function assertEnsureOk(array $schema, ?array $input, ?array $output) {
+    assoc::ensure_schema($input, $schema);
+    self::assertSame($output, $input);
+  }
+
+  static function assertEnsureFail(array $schema, ?array $input, ?array $output) {
+    self::assertException(ValueException::class, function() use ($input, $schema) {
+      assoc::ensure_schema($input, $schema);
+    });
+  }
+
+  function testEnsureSchema() {
+    self::assertEnsureOk([
+      "string" => "string",
+      "int" => "int",
+    ], [
+      "string" => 5,
+      "int" => "42",
+    ], [
+      "string" => "5",
+      "int" => 42,
+    ]);
+  }
+
+  const SCHEMA_S = ["s" => "string"];
+  const SCHEMA_SD = ["s" => ["string", null]];
+  const SCHEMA_SND = ["s" => ["string", "not null"]];
+  const SCHEMA_RS = ["s" => ["string", "required" => true]];
+  const SCHEMA_RSD = ["s" => ["string", null, "required" => true]];
+  const SCHEMA_RSND = ["s" => ["string", "not null", "required" => true]];
+  const SCHEMA_NS = ["s" => "?string"];
+  const SCHEMA_NSD = ["s" => ["?string", null]];
+  const SCHEMA_NSND = ["s" => ["?string", "not null"]];
+  const SCHEMA_NRS = ["s" => ["?string", "required" => true]];
+  const SCHEMA_NRSD = ["s" => ["?string", null, "required" => true]];
+  const SCHEMA_NRSND = ["s" => ["?string", "not null", "required" => true]];
+
+  function testEnsureSchema2() {
+    self::assertEnsureOk(self::SCHEMA_S,   [], []);
+    self::assertEnsureFail(self::SCHEMA_S, ["s" => null], ["s" => null]);
+    self::assertEnsureOk(self::SCHEMA_S,   ["s" => "not null"], ["s" => "not null"]);
+    self::assertEnsureOk(self::SCHEMA_NS,  [], []);
+    self::assertEnsureOk(self::SCHEMA_NS,  ["s" => null], ["s" => null]);
+    self::assertEnsureOk(self::SCHEMA_NS,  ["s" => "not null"], ["s" => "not null"]);
+
+    self::assertEnsureOk(self::SCHEMA_SD,   [], []);
+    self::assertEnsureFail(self::SCHEMA_SD, ["s" => null], ["s" => null]);
+    self::assertEnsureOk(self::SCHEMA_SD,   ["s" => "not null"], ["s" => "not null"]);
+    self::assertEnsureOk(self::SCHEMA_NSD,  [], []);
+    self::assertEnsureOk(self::SCHEMA_NSD,  ["s" => null], ["s" => null]);
+    self::assertEnsureOk(self::SCHEMA_NSD,  ["s" => "not null"], ["s" => "not null"]);
+
+    self::assertEnsureOk(self::SCHEMA_SND,  [], ["s" => "not null"]);
+    self::assertEnsureOk(self::SCHEMA_SND,  ["s" => null], ["s" => "not null"]);
+    self::assertEnsureOk(self::SCHEMA_SND,  ["s" => "not null"], ["s" => "not null"]);
+    self::assertEnsureOk(self::SCHEMA_NSND, [], ["s" => "not null"]);
+    self::assertEnsureOk(self::SCHEMA_NSND, ["s" => null], ["s" => null]);
+    self::assertEnsureOk(self::SCHEMA_NSND, ["s" => "not null"], ["s" => "not null"]);
+
+    self::assertEnsureFail(self::SCHEMA_RS,  [], []);
+    self::assertEnsureFail(self::SCHEMA_RS,  ["s" => null], []);
+    self::assertEnsureOk(self::SCHEMA_RS,    ["s" => "not null"], ["s" => "not null"]);
+    self::assertEnsureFail(self::SCHEMA_NRS, [], []);
+    self::assertEnsureOk(self::SCHEMA_NRS,   ["s" => null], ["s" => null]);
+    self::assertEnsureOk(self::SCHEMA_NRS,   ["s" => "not null"], ["s" => "not null"]);
+
+    self::assertEnsureFail(self::SCHEMA_RSD, [], []);
+    self::assertEnsureFail(self::SCHEMA_RSD, ["s" => null], []);
+    self::assertEnsureOk(self::SCHEMA_RSD, ["s" => "not null"], ["s" => "not null"]);
+    self::assertEnsureFail(self::SCHEMA_NRSD, [], []);
+    self::assertEnsureOk(self::SCHEMA_NRSD, ["s" => null], ["s" => null]);
+    self::assertEnsureOk(self::SCHEMA_NRSD, ["s" => "not null"], ["s" => "not null"]);
+
+    self::assertEnsureOk(self::SCHEMA_RSND, [], ["s" => "not null"]);
+    self::assertEnsureOk(self::SCHEMA_RSND, ["s" => null], ["s" => "not null"]);
+    self::assertEnsureOk(self::SCHEMA_RSND, ["s" => "not null"], ["s" => "not null"]);
+    self::assertEnsureOk(self::SCHEMA_NRSND, [], ["s" => "not null"]);
+    self::assertEnsureOk(self::SCHEMA_NRSND, ["s" => null], ["s" => null]);
+    self::assertEnsureOk(self::SCHEMA_NRSND, ["s" => "not null"], ["s" => "not null"]);
+  }
+}
diff --git a/php/tests/php/types/scalarTest.php b/php/tests/php/types/scalarTest.php
new file mode 100644
index 0000000..44bd667
--- /dev/null
+++ b/php/tests/php/types/scalarTest.php
@@ -0,0 +1,60 @@
+<?php
+namespace nulib\php\types;
+
+use nulib\tests\TestCase;
+use nulib\ValueException;
+
+class scalarTest extends TestCase {
+  function testCheckSchema() {
+    self::assertTrue(scalar::check_schema(5, "int"));
+    self::assertTrue(scalar::check_schema(5, "string"));
+    self::assertTrue(scalar::check_schema(5, "float"));
+
+    self::assertTrue(scalar::check_schema(5, "int", true));
+    self::assertFalse(scalar::check_schema(5, "string", true));
+    self::assertFalse(scalar::check_schema(5, "float", true));
+
+    self::assertTrue(scalar::check_schema("5", "int"));
+    self::assertTrue(scalar::check_schema("5", "string"));
+    self::assertTrue(scalar::check_schema("5", "float"));
+
+    self::assertFalse(scalar::check_schema("5", "int", true));
+    self::assertTrue(scalar::check_schema("5", "string", true));
+    self::assertFalse(scalar::check_schema("5", "float", true));
+
+    self::assertFalse(scalar::check_schema("bad format", "int"));
+  }
+
+  function testEnsureSchema() {
+    $v = 5; scalar::ensure_schema($v, "int");
+    self::assertSame(5, $v);
+    $v = "5"; scalar::ensure_schema($v, "int");
+    self::assertSame(5, $v);
+    $v = "5.0"; scalar::ensure_schema($v, "int");
+    self::assertSame(5, $v);
+    $v = 5.0; scalar::ensure_schema($v, "int");
+    self::assertSame(5, $v);
+    
+    $v = 5; scalar::ensure_schema($v, "string");
+    self::assertSame("5", $v);
+    $v = "5"; scalar::ensure_schema($v, "string");
+    self::assertSame("5", $v);
+    $v = "5.0"; scalar::ensure_schema($v, "string");
+    self::assertSame("5.0", $v);
+    $v = 5.0; scalar::ensure_schema($v, "string");
+    self::assertSame("5", $v);
+
+    $v = 5; scalar::ensure_schema($v, "float");
+    self::assertSame(5.0, $v);
+    $v = "5"; scalar::ensure_schema($v, "float");
+    self::assertSame(5.0, $v);
+    $v = "5.0"; scalar::ensure_schema($v, "float");
+    self::assertSame(5.0, $v);
+    $v = 5.0; scalar::ensure_schema($v, "float");
+    self::assertSame(5.0, $v);
+
+    self::assertException(ValueException::class, function() {
+      $v = "bad format"; scalar::ensure_schema($v, "int");
+    });
+  }
+}