With this function You can compress Your PHP source code.

<?php

function compress_php_src($src) {
    // Whitespaces left and right from this signs can be ignored
    static $IW = array(
        T_CONCAT_EQUAL,             // .=
        T_DOUBLE_ARROW,             // =>
        T_BOOLEAN_AND,              // &&
        T_BOOLEAN_OR,               // ||
        T_IS_EQUAL,                 // ==
        T_IS_NOT_EQUAL,             // != or <>
        T_IS_SMALLER_OR_EQUAL,      // <=
        T_IS_GREATER_OR_EQUAL,      // >=
        T_INC,                      // ++
        T_DEC,                      // --
        T_PLUS_EQUAL,               // +=
        T_MINUS_EQUAL,              // -=
        T_MUL_EQUAL,                // *=
        T_DIV_EQUAL,                // /=
        T_IS_IDENTICAL,             // ===
        T_IS_NOT_IDENTICAL,         // !==
        T_DOUBLE_COLON,             // ::
        T_PAAMAYIM_NEKUDOTAYIM,     // ::
        T_OBJECT_OPERATOR,          // ->
        T_DOLLAR_OPEN_CURLY_BRACES, // ${
        T_AND_EQUAL,                // &=
        T_MOD_EQUAL,                // %=
        T_XOR_EQUAL,                // ^=
        T_OR_EQUAL,                 // |=
        T_SL,                       // <<
        T_SR,                       // >>
        T_SL_EQUAL,                 // <<=
        T_SR_EQUAL,                 // >>=
    );
    if(is_file($src)) {
        if(!$src = file_get_contents($src)) {
            return false;
        }
    }
    $tokens = token_get_all($src);
    
    $new = "";
    $c = sizeof($tokens);
    $iw = false; // ignore whitespace
    $ih = false; // in HEREDOC
    $ls = "";    // last sign
    $ot = null;  // open tag
    for($i = 0; $i < $c; $i++) {
        $token = $tokens[$i];
        if(is_array($token)) {
            list($tn, $ts) = $token; // tokens: number, string, line
            $tname = token_name($tn);
            if($tn == T_INLINE_HTML) {
                $new .= $ts;
                $iw = false;
            } else {
                if($tn == T_OPEN_TAG) {
                    if(strpos($ts, " ") || strpos($ts, "\n") || strpos($ts, "\t") || strpos($ts, "\r")) {
                        $ts = rtrim($ts);
                    }
                    $ts .= " ";
                    $new .= $ts;
                    $ot = T_OPEN_TAG;
                    $iw = true;
                } elseif($tn == T_OPEN_TAG_WITH_ECHO) {
                    $new .= $ts;
                    $ot = T_OPEN_TAG_WITH_ECHO;
                    $iw = true;
                } elseif($tn == T_CLOSE_TAG) {
                    if($ot == T_OPEN_TAG_WITH_ECHO) {
                        $new = rtrim($new, "; ");
                    } else {
                        $ts = " ".$ts;
                    }
                    $new .= $ts;
                    $ot = null;
                    $iw = false;
                } elseif(in_array($tn, $IW)) {
                    $new .= $ts;
                    $iw = true;
                } elseif($tn == T_CONSTANT_ENCAPSED_STRING
                       || $tn == T_ENCAPSED_AND_WHITESPACE)
                {
                    if($ts[0] == '"') {
                        $ts = addcslashes($ts, "\n\t\r");
                    }
                    $new .= $ts;
                    $iw = true;
                } elseif($tn == T_WHITESPACE) {
                    $nt = @$tokens[$i+1];
                    if(!$iw && (!is_string($nt) || $nt == '$') && !in_array($nt[0], $IW)) {
                        $new .= " ";
                    }
                    $iw = false;
                } elseif($tn == T_START_HEREDOC) {
                    $new .= "<<<S\n";
                    $iw = false;
                    $ih = true; // in HEREDOC
                } elseif($tn == T_END_HEREDOC) {
                    $new .= "S;";
                    $iw = true;
                    $ih = false; // in HEREDOC
                    for($j = $i+1; $j < $c; $j++) {
                        if(is_string($tokens[$j]) && $tokens[$j] == ";") {
                            $i = $j;
                            break;
                        } else if($tokens[$j][0] == T_CLOSE_TAG) {
                            break;
                        }
                    }
                } elseif($tn == T_COMMENT || $tn == T_DOC_COMMENT) {
                    $iw = true;
                } else {
                    if(!$ih) {
                        $ts = strtolower($ts);
                    }
                    $new .= $ts;
                    $iw = false;
                }
            }
            $ls = "";
        } else {
            if(($token != ";" && $token != ":") || $ls != $token) {
                $new .= $token;
                $ls = $token;
            }
            $iw = true;
        }
    }
    return $new;
}

?>

For example:
<?php

$src = <<<EOT
<?php
// some comment
for ( $i = 0; $i < 99; $i ++ ) {
   echo "i=${ i }\n";
   /* ... */
}
/** ... */
function abc() {
   return   "abc";
};

abc();
?>
<h1><?= "Some text " . str_repeat("_-x-_ ", 32);;; ?></h1>
EOT;
var_dump(compress_php_src($src));
?>

And the result is:
string(125) "<?php for(=0;<99;++){echo "i=\n";}function abc(){return "abc";};abc(); ?>
<h1><?="Some text ".str_repeat("_-x-_ ",32)?></h1>"

If you wish to just remove excess whitespace from a string, see the example "Strip whitespace" in the preg_replace documentation (http://www.php.net/manual/en/function.preg-replace.php).

Beware that this function uses the output buffering mechanism.

If you give a 'stream wrapped' path as argument, anything echoed by the stream wrapper during this call (e.g. trace messages) won't be displayed to the screen but will be inserted in php_strip_whitespace's result.

If you execute this stripped code later, it will display the messages which should have been output during php_strip_whitespace's execution !

i notice that on 45=75kb php file compressed using php_strip_whitespace i got slowest speed results in my apache benchmark  .bat tests so doing on a normal php file 10 tests and another 10 tests on a compressed one ,calculating the math average value  I got fastest results on  normal php files.

well,seeing that results i think  SO ,NICE,BUT IF WE COMBINE THESE "METHODS" : what if i use a partial minified method using this function ????

here is the code:
(if you run this in xampp and you are beginner you got a blank page in firefox  ,but if you right click it then you click on the option "view source" you'll get the php partial stripped by comments and tabs) :

<?php
/*   hi there !!!
here are the comments */
//another try

echo removecomments('index.php');

/*   hi there !!!
here are the comments */
//another try
function removecomments($f){
    $w=Array(';','{','}');
    $ts = token_get_all(php_strip_whitespace($f));
    $s='';
    foreach($ts as $t){
        if(is_array($t)){
            $s .=$t[1];
        }else{
            $s .=$t;
            if( in_array($t,$w) ) $s.=chr(13).chr(10);
        }
    }

    return $s;
}

?>

I was looking earlier for a way to strip php comments from my source files but didn't come up with much.  I wrote the following function to do the trick using the tokenizer.  I've tested in on an entire phpMyAdmin install and it worked fine afterward... so it should be good to go.  You may also specify any number of tokens to strip such as T_WHITESPACE rather the default of T_COMMENT and T_DOC_COMMENT.

Hopefully someone finds it useful.

<?php

function strip_tokens($code) {

    $args = func_get_args();
    $arg_count = count($args);
    
    // if no tokens to strip have been specified then strip comments by default
    if( $arg_count === 1 ) {
        $args[1] = T_COMMENT;
        $args[2] = T_DOC_COMMENT;
    }

    // build a keyed array of tokens to strip
    for( $i = 1; $i < $arg_count; ++$i )
        $strip[ $args[$i] ] = true;

    // set a keyed array of newline characters used to preserve line numbering
    $newlines = array("\n" => true, "\r" => true);

    $tokens = token_get_all($code);

    reset($tokens);

    $return = '';

    $token = current($tokens);
    
    while( $token ) {

        if( !is_array($token) )

            $return.= $token;

        elseif(    !isset($strip[ $token[0] ]) )

            $return.= $token[1];

        else {
            
            // return only the token's newline characters to preserve line numbering
            for( $i = 0, $token_length = strlen($token[1]); $i < $token_length; ++$i )
                if( isset($newlines[ $token[1][$i] ]) )
                    $return.= $token[1][$i];

        }

        $token = next($tokens);

    } // while more tokens

    return $return;

} // function

?>