check a php variable with a generic function that will work with any variable

Question

I'm trying to make a PHP function that wraps around a variable that will check the variable value and change it if it matches another variable. I'm sure I'm doing it wrong, but...

Here's what I have so far:

<?php 

function Clear_Value(){

    $val='NONE';

    if(this== $val){ this=='';}

    };

$one    = 'One';
$two    = 'Two';
$three  = 'NONE';
$four   = 'Four';

Clear_Value($one);
Clear_Value($two);
Clear_Value($three);
Clear_Value($four);

echo $one.'<br>';
echo $two.'<br>';
echo $three.'<br>';
echo $four.'<br>';

?>

The output I'm going for would be:

One
Two

Four

I hope that's clear. I'm still learning functions in php so any pointers would be great.

Thanks

You can only use this (which should be $this) within a class. — nickb
– nickb, Commented Apr 23, 2012 at 17:33

Cal · Accepted Answer · 2012-04-23 17:32:00Z

3

You need to pass an argument by reference:

function Clear_Value(&$arg){

    if ($arg == 'NONE') $arg = '';
}

This way, the function can modify the variable's contents.

Live example: http://ideone.com/igHc5

answered Apr 23, 2012 at 17:32

Cal

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3 Comments

John Cartwright Over a year ago

This is a good approach (given current context) since this function can be used as a callback (i.e., array_map) instead of dealing with several variables.

Cal Over a year ago

That means you have two functions called Clear_Value() - remove your own one and just add this one.

Monty Over a year ago

Yeah, I did have two. Thanks! this is what I was after. So $arg could be anything, right? Also, what the PHP term for this so I can read up on it more?

MireSVK · Accepted Answer · 2012-04-23 17:37:41Z

1

what your constant this stands for?

you have to create some input variable in your function and use & prefix (refers to variable in memory)

function Clear_Value(&$var){

 $val='NONE';

 if($var == $val) 
  $var = '';

};

and another thing, if you want to change value of a variable, you use just single "=". i recommend you to see basics of syntax at php.net

sorry for my english

answered Apr 23, 2012 at 17:37

MireSVK

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Comments

Mohan Shanmugam · Accepted Answer · 2012-04-23 17:44:07Z

1

I am not sure what you expect here.

But when you execute this program it will show undefined variable error.

Try my sample changed code:-

 <?php 

   function Clear_Value($sam){

   $val='NONE';

   if($sam== $val){ $sam=='';}
   echo $sam.'<br>';

   };

   $one    = 'One';
   $two    = 'Two';
   $three  = 'NONE';
   $four   = 'Four';

   Clear_Value($one);
   Clear_Value($two);
   Clear_Value($three);
   Clear_Value($four);
   /*
   echo $one.'<br>';
   echo $two.'<br>';
   echo $three.'<br>';
   echo $four.'<br>';
   */
   ?>

answered Apr 23, 2012 at 17:44

Mohan Shanmugam

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