In PHP, How to call function in string?

Question 1

say,string is:

$str="abcdefg foo() hijklmopqrst";

How to let php call foo() and insert the return string to this string?

Question 2

$str="abcdefg foo() hijklmopqrst";
function foo() {return "bar";}

$replaced = preg_replace_callback("~([a-z]+)()~", 
     function ($m){
          return $m[1]();
     }, $str);

output:

$replaced == 'abcdefg bar hijklmopqrst';

This will allow any lower-case letters as function name. If you need any other symbols, add them to the pattern, i.e. [a-zA-Z_].

Be VERY careful which functions you allow to be called. You should at least check if $m[1] contains a whitelisted function to not allow remote code injection attacks.

$allowedFunctions = array("foo", "bar" /*, ...*/);

$replaced = preg_replace_callback("~([a-z]+)()~", 
     function ($m) use ($allowedFunctions) {
          if (!in_array($m[1], $allowedFunctions))
              return $m[0]; // Don't replace and maybe add some errors.

          return $m[1]();
     }, $str);

Testrun on "abcdefg foo() bat() hijklmopqrst" outputs "abcdefg bar bat() hijklmopqrst".

Optimisation for whitelisting approach (building pattern dynamically from allowed function names, i.e. (foo|bar).

$allowedFunctions = array("foo", "bar");

$replaced = preg_replace_callback("~(".implode("|",$allowedFunctions).")()~", 
     function ($m) {
          return $m[1]();
     }, $str);

Question 3

you should create the var in the class, not in the function, because when the function end the variable will be unset (due to function termination)...

class helloWorld {

private $var;

function sayHello() {
     echo "Hello";
     $this->var = "World";
}

function sayWorld() {
     echo $this->var;
}


}
?>

If you declare the Variable as public, it's accessible directly by all the others classes, whereas if you declare the variable as private, it's accessible only in the same class..

<?php
 Class First {
  private $a;
  public $b;

  public function create(){
    $this->a=1; //no problem
    $thia->b=2; //no problem
  }

  public function geta(){
    return $this->a;
  }
  private function getb(){
    return $this->b;
  }
 }

 Class Second{

  function test(){
    $a=new First; //create object $a that is a First Class.
    $a->create(); // call the public function create..
    echo $a->b; //ok in the class the var is public and it's accessible by everywhere
    echo $a->a; //problem in hte class the var is private
    echo $a->geta(); //ok the A value from class is get through the public function, the value $a in the class is not dicrectly accessible
    echo $a->getb(); //error the getb function is private and it's accessible only from inside the class
  }
}
?>

Question 4

Here's what worked best for me when trying to script this (in case anyone else comes across this like I did):

$ pecl -d php_suffix=5.6 install <package>
$ pecl uninstall -r <package>

$ pecl -d php_suffix=7.0 install <package>
$ pecl uninstall -r <package>

$ pecl -d php_suffix=7.1 install <package>
$ pecl uninstall -r <package>

The -d php_suffix=<version> piece allows you to set config values at run time vs pre-setting them with pecl config-set. The uninstall -r bit does not actually uninstall it (from the docs):

vagrant@homestead:~$ pecl help uninstall
pecl uninstall [options] [channel/]<package> ...
Uninstalls one or more PEAR packages.  More than one package may be
specified at once.  Prefix with channel name to uninstall from a
channel not in your default channel (pecl.php.net)

Options:
  ...
  -r, --register-only
        do not remove files, only register the packages as not installed
  ...

The uninstall line is necessary otherwise installing it will remove any previously installed version, even if it was for a different PHP version (ex: Installing an extension for PHP 7.0 would remove the 5.6 version if the package was still registered as installed).

Question 5

That's what abstract classes are for. An abstract class basically says: Whoever is inheriting from me, must have this function (or these functions).

abstract class whale
{

  function __construct()
  {
    // some code here
  }

  function myfunc()
  {
    $this->test();
  }

  abstract function test();
}


class fish extends whale
{
  function __construct()
  {
    parent::__construct();
  }

  function test()
  {
    echo "So you managed to call me !!";
  }

}


$fish = new fish();
$fish->test();
$fish->myfunc();

Question 6

Never used any of those, but they look interesting..

Take a look at Gearman as well.. more overhead in systems like these but you get other cool stuff :) Guess it depends on your needs ..

In PHP, How to call function in string?

Answers

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