PHP: equivalent of MySQL's function SUBSTRING_INDEX ?

Question

I love the SUBSTRING_INDEX function in MySQL, especially because you can use negative indexes to start searching from the right side of the string.

Is there an equiv

Answer 1

There's no single library function that gets you this same functionality, but you can get a one-liner:

$str = "www.mysql.com";
echo implode('.', array_slice(explode('.', $str), 0, 2)); // prints "www.mysql"
echo implode('.', array_slice(explode('.', $str), -2));   // prints "mysql.com"

Easily turn this into a function:

function substring_index($subject, $delim, $count){
    if($count < 0){
        return implode($delim, array_slice(explode($delim, $subject), $count));
    }else{
        return implode($delim, array_slice(explode($delim, $subject), 0, $count));
    }
}

Answer 2

If you need equivalent only for SUBSTRING_INDEX(str, delim, 1), you can use:

list($str,) = explode($delim, $str);

Answer 3

function substring_index($subject, $delim, $count){
    if($count < 0){
        return implode($delim, array_slice(explode($delim, $subject), $count));
    }else{
        return implode($delim, array_slice(explode($delim, $subject), 0, $count));
    }
}

Answer 4

I was curious and tested another method using a preg/match setup, then refactored it to allow for any number of delimiters/count. I added in the count check the other example was using, but I would probably also recommend some kind of sanitization of the delimiter field.

function substring_index($subject, $delim, $count){
  if($count < 0){
    $notRe = '[^\\'.$delim.']*';
    $elem = array();
    for($x=1;$x<=$count;$x++){
      array_push($elem,$notRe);
    }
    $re = '/^('.implode('\\'.$delim,$elem).')/';
    preg_match($re, $subject,$m);
    if(count($m) == 2) {
      return $m[1];
    }
  }
}

Answer 5

I think

string strstr ( string $haystack , mixed $needle [, bool $before_needle = false ] )

is the right php function for you.

strstr — Finds the first occurrence of a string

<?php
$email  = 'name@example.com';
$domain = strstr($email, '@');
echo $domain; // prints @example.com

$user = strstr($email, '@', true); // As of PHP 5.3.0
echo $user; // prints name
?>