$re = '/(^function|[ ;}\n=]function)(|[ ]+[a-zA-Z_0-9]*[ ]*)([(]([^()]|(?3))*[)])[ \n]*([{]([^{}]|(?5))*[}])/';
$str = 'function(hjsjds(asasa)){kldsklsdjskhd ={ b = function(){ }; } ;ksdjdskdk jksjdsdsdksnn}
';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php