Replace variable by another variable in PHP

Question

Here is my situation, let's say i have two variables:

$a = "Peter";
$b = "tall";

Then, i can combine this by

$c = " $a is very $b ";

which give me the string : "Peter is very tall"

However, if i have another variable $e passed to my function, and the string is " $a is very $b " then, i print out $e, it just show me " $a is very $b ";

What i expected is "Peter is very tall", because $e is equal to $c.

This is the whole logic flow:

$e = " $a is very $b ";
getMsg($e);
function getMsg($e){
  $a = "Peter";
  $b = "tall";
  $c = " $a is very $b ";
  echo $c //Peter is very tall
  echo $e //$a is very $b
}

How can i achieve this function?

Turn on error reporting and you will see something like Notice: Undefined variable: a in ... and Notice: Undefined variable: b in ... . $a and $b are undefined in your $e line. And echo $e will probably output " is very ". (Also, your echos are missing a ;) php.net/manual/en/language.variables.scope.php — user8034901
– user8034901, Commented Sep 27, 2019 at 11:21
You should never use double quotes for string, always single ones. If you try to rewrite your code without double quotes and concatenate strings by yourself, I think you will easily find what's wrong — Will
– Will, Commented Sep 27, 2019 at 12:06

suspectus · Accepted Answer · 2019-09-27 11:46:28Z

2

You could use sprintf sprintf documentation. The %s symbols are string tokens that get substituted in the format string (the 1st param to sprintf).

$e = "%s is very %s";
getMsg($e);
function getMsg($e){
  $a = "Peter";
  $b = "tall";
  echo sprintf($e, $a, $b);
}

Or a less coupled version of the getMsg() function:

function getMsg($msg,$name,$is){
  echo sprintf($msg, $name, $is);
}  
getMsg("%s is very %s", "Peter", "tall");

answered Sep 27, 2019 at 11:46

suspectus

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3 Comments

Will Over a year ago

You should never use double quotes for string, always single ones. That's what caused OPs confusion in the first place

suspectus Over a year ago

Not always. e.g. $a='hello'; echo '$a'

Will Over a year ago

Yes, that the whole point : that makes you think about if you need quotes or not. You can't just use them everywhere. In that exemple you absolutely don't need quotes, simple or double ones !

Ajay Shukla · Accepted Answer · 2019-09-27 11:26:56Z

0

Please try this code. I hope this is what you want.

<?php
// Your code here!
 $a = "Peter";
  $b = "tall";
$e = $a."is very".$b;
getMsg($e,$a,$b);
function getMsg($e,$a,$b)
{
 $c = $a."is very".$b;
  echo $c;
 echo $e;
}
?>

answered Sep 27, 2019 at 11:26

Ajay Shukla

113 bronze badges

1 Comment

Ajay Shukla Over a year ago

You need to check the scope of variables and also you need to check you function definition and how you're calling your function.

Vaibhavi S. · Accepted Answer · 2019-09-27 11:30:13Z

0

Try this. It should work fine. You need to Define $a and $b outside the function.

function getString($a,$b,$e){

  $c = " $a is very $b ";
  echo $c;
  echo '<br/>'.$e;
}
$a = "Peter";
$b = "tall";
$e = " $a is very $b ";
$response = getString($a,$b,$e);

OUTPUT :

Peter is very tall 
Peter is very tall

answered Sep 27, 2019 at 11:30

Vaibhavi S.

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