PHP - replace a string with a variable named like the string

Question

Hi

so the string is like this:

"bla bla bla {VARIABLE} bla bla"

when I use this string somewhere in a function I want to replace {VARIABLE} with $variable (or any other uppercase strings with wrapped within {} charcters). $variable (and any other variables) will be defined inside that function

Can i do this?

Answer 1

$TEST = 'one';
$THING = 'two';
$str = "this is {TEST} a {THING} to test";

$result = preg_replace('/\{([A-Z]+)\}/e', "$$1", $str);

Answer 2

Use a regular expression to find all substitutions, then iterate over the result and replace them. Be sure to only allow variables you would want to expose.

// white list of variables
$allowed_variables = array("test", "variable", "not_POST", "not_GET",); 

preg_match("#(\{([A-Z]+?)\}#", $text, $matches);

// not sure the result is in [1], do a var_dump
while($matches[1] as $variable) { 
    $variable = strtolower($variable);

    // only allow white listed variables
    if(!in_array($variable, $allowed_variables)) continue; 

    $text = str_replace("{".$match."}", $$match, $text);
}

Answer 3

This will work....

$FOO = 'Salt';
$BAR = 'Peppa';
$string = '{FOO} and {BAR}';
echo preg_replace( '/\{([A-Z]+)\}/e', "$$1", $string );

but it just seems like an awful idea.

Answer 4

The following is another solution, but I agree with other folks who are dubious about whether this is a wise thing for you to do.

<?php

$string = "bla bla bla {VARIABLE} bla bla";
$VARIABLE = "foo";

function var_repl($matches)
{
  return $GLOBALS[$matches[1]];
}

echo preg_replace_callback("/{(\w+)}/", "var_repl", $string);