in_array
    (PHP 4, PHP 5)
in_array -- Checks if a value exists in an array
Description
bool 
in_array ( mixed needle, array haystack [, bool strict] )
     Searches haystack for
     needle and returns TRUE
     if it is found in the array, FALSE otherwise.
    
     If the third parameter strict is set to
     TRUE then the in_array() function
     will also check the types of
     the needle in the haystack.
    
Note: 
      If needle is a string, the comparison is done in
      a case-sensitive manner.
     
Note: 
      In PHP versions before 4.2.0 needle was not
      allowed to be an array.
     
     
Example 1. in_array() example 
<?php $os = array("Mac", "NT", "Irix", "Linux"); if (in_array("Irix", $os)) {     echo "Got Irix"; } if (in_array("mac", $os)) {     echo "Got mac"; } ?>
 |  
 
       The second condition fails because in_array()
       is case-sensitive, so the program above will display:
        | 
    
     
Example 2. in_array() with strict example 
<?php $a = array('1.10', 12.4, 1.13);
  if (in_array('12.4', $a, true)) {     echo "'12.4' found with strict check\n"; }
  if (in_array(1.13, $a, true)) {     echo "1.13 found with strict check\n"; } ?>
 |  
 The above example will output: 1.13 found with strict check  |  
  | 
    
     
Example 3. in_array() with an array as needle 
<?php $a = array(array('p', 'h'), array('p', 'r'), 'o');
  if (in_array(array('p', 'h'), $a)) {     echo "'ph' was found\n"; }
  if (in_array(array('f', 'i'), $a)) {     echo "'fi' was found\n"; }
  if (in_array('o', $a)) {     echo "'o' was found\n"; } ?>
 |  
 The above example will output: 'ph' was found
  'o' was found  |  
  | 
    
     See also array_search(),
     array_key_exists(), and
     isset().