Simple tokenizer which only splits on space character, while maintaining context for single or double-quoted strings. Uses include creation of very basic DSLs in PHP.

simpletokenizer.php

<?php

for($x=0;$x<strlen($argv[1]);$x++){
    $tokens[] = getNextToken(substr($argv[1],$x),$x);
}

print_r($tokens);

function getNextToken($input,&$prefix){

	$insidedq = $insidesq = false;

	$buff = '';
	for($x=0;$x<strlen($input);$x++){
		switch($input[$x]){
			case '"':
				if($insidesq){
					$buff.=$input[$x];
					continue;
				}
				elseif($insidedq){
					break 2;
				}
				elseif(empty($buff)){
					$insidedq = true;
				}
				else{
					$buff .= $input[$x];
				}
				break;
			case "'":
				if($insidedq){
					$buff.=$input[$x];
					continue;
				}
				elseif($insidesq){
					break 2;
				}
				elseif(empty($buff)){
					$insidesq = true;
				}
				else{
					$buff .= $input[$x];
				}
				break;
			case ' ':
				if($insidedq || $insidesq){
					$buff .= $input[$x];
				}
				elseif(empty($buff)){
					continue;
				}
				else{
					break 2;
				}
				break;
			default:
				$buff .= $input[$x];
				break;
		}
	}
	$prefix += $x;
	return $buff;
}

only minimal amount of testing has been done