How to get a substring between two strings in PHP?

Regular expressions is the way to go:

$str = 'before-str-after';
if (preg_match('/before-(.*?)-after/', $str, $match) == 1) {
    echo $match[1];
}

onlinePhp

If the strings are different (ie: [foo] & [/foo]), take a look at this post from Justin Cook. I copy his code below:

function get_string_between($string, $start, $end){
    $string = ' ' . $string;
    $ini = strpos($string, $start);
    if ($ini == 0) return '';
    $ini += strlen($start);
    $len = strpos($string, $end, $ini) - $ini;
    return substr($string, $ini, $len);
}

$fullstring = 'this is my [tag]dog[/tag]';
$parsed = get_string_between($fullstring, '[tag]', '[/tag]');

echo $parsed; // (result = dog)