ctype_digit
    (PHP 4 >= 4.0.4, PHP 5)
ctype_digit -- Check for numeric character(s)
Description
bool 
ctype_digit ( string text )
   Checks if all of the characters in the provided string,
   text, are numerical.
  
Return Values
   Returns TRUE if every character in text is 
   a decimal digit, FALSE otherwise.
  
Examples
   
Example 1. A ctype_digit() example 
<?php $strings = array('1820.20', '10002', 'wsl!12'); foreach ($strings as $testcase) {     if (ctype_digit($testcase)) {         echo "The string $testcase consists of all digits.\n";     } else {         echo "The string $testcase does not consist of all digits.\n";     } } ?>
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 The above example will output: The string 1820.20 does not consists of all digits.
The string 10002 consists of all digits.
The string wsl!12 does not consists of all digits.  |  
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