PHP: Concatenate a leading zero to single digit numbers in string

Question

I have this sample string: hello77boss2america-9-22-fr99ee-9. A leading 0 should be added in front of all the single digit numbers of the string. The result should

Answer 1

You can use preg_replace to find the lone digits and replace them, something like...

<?php
echo preg_replace(
    '~(?<!\d)(\d)(?!\d)~',
    '0$1',
    'hello77boss2america-9-22-fr99ee-9'
); //hello77boss02america-09-22-fr99ee-09

Here's a slightly more descriptive version.

<?php
$callback = function($digit) {

    $digit = $digit[0];

    if (1 == strlen($digit)) {
        $digit = "0$digit";
    }

    return $digit;
};

echo preg_replace_callback('~\d+~', $callback, 'hello77boss2america-9-22-fr99ee-9');
// hello77boss02america-09-22-fr99ee-09