   #PHP Manual Types Types Integers

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Booleans

   This is the easiest type. A boolean expresses a truth value. It can be
   either TRUE or FALSE.

     Note: The boolean type was introduced in PHP 4.

Syntax

   To specify a boolean literal, use either the keyword TRUE or FALSE.
   Both are case-insensitive.

   <?php
   $foo = True; // assign the value TRUE to $foo
   ?>

   Usually you use some kind of operator which returns a boolean value,
   and then pass it on to a control structure.

   <?php
   // == is an operator which test
   // equality and returns a boolean
   if ($action == "show_version") {
       echo "The version is 1.23";
   }
   // this is not necessary...
   if ($show_separators == TRUE) {
       echo "<hr>\n";
   }
   // ...because you can simply type
   if ($show_separators) {
       echo "<hr>\n";
   }
   ?>

Converting to boolean

   To explicitly convert a value to boolean, use either the (bool) or the
   (boolean) cast. However, in most cases you do not need to use the
   cast, since a value will be automatically converted if an operator,
   function or control structure requires a boolean argument.

   See also Type Juggling.

   When converting to boolean, the following values are considered FALSE:

     * the boolean FALSE itself
     * the integer 0 (zero)
     * the float 0.0 (zero)
     * the empty string, and the string "0"
     * an array with zero elements
     * an object with zero member variables
     * the special type NULL (including unset variables)

   Every other value is considered TRUE (including any resource).

   Warning

   -1 is considered TRUE, like any other non-zero (whether negative or
   positive) number!

   <?php
   echo gettype((bool) "");        // bool(false)
   echo gettype((bool) 1);         // bool(true)
   echo gettype((bool) -2);        // bool(true)
   echo gettype((bool) "foo");     // bool(true)
   echo gettype((bool) 2.3e5);     // bool(true)
   echo gettype((bool) array(12)); // bool(true)
   echo gettype((bool) array());   // bool(false)
   ?>
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