How to convert a String to Integer and test it?

I've a problem. I'm scrapping a txt file and extracting an ID. The problem is that the data is not consistent and I hav开发者_如何学Goe to evaluate the data.

Here is some code:

$a = "34";
$b = " 45";
$c = "ddd556z";


if (  ) {

    echo "INTEGER";
} else{ 

    echo "STRING";
}

I need test if the values $a, $b or $c are Integers. What is the best way of doing this? I have tested to "trim" and the use "is_int" but is not working as expected.

Can someone give me some clues?

The example below will work even if your "int" is a string $a = "number";

is_numeric()

or

preg_match( '/^-?[0-9]+$/' , $var )  // negative number © Piskvor

or

intval($var) == $var

or (same as last)

(int) $var == $var

http://www.php.net/manual/en/function.ctype-digit.php

<?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";
    }
}

// will output
//The string 1820.20 does not consist of all digits.
//The string 10002 consists of all digits.
//The string wsl!12 does not consist of all digits.

<?
$a = 34;
if (is_int($a)) {
    echo "is integer";
} else {
    echo "is not an integer";
}
?>

$a="34";

will not validate as int ;)