php html include str-replace file-get-contents

How to include file in PHP with user defined variable

I am trying to include file in string replace but in output i am getting string not the final output.

analytic.php

<?php echo "<title> Hello world </title>"; ?>

head.php

<?php include "analytic.php"; ?>

index.php

string = " <head> </head>";
$headin = file_get_contents('head.php');
$head = str_replace("<head>", "<head>". $headin, $head);
echo $head;

Output i am getting :

 <head><?php include "analytic.php"; ?> </head>

Output i need :

 <head><title> Hello world </title> </head>

Note : Please do not recommend using analytic.php directly in index.php because head.php have some important code and it has to be merged analytic.php with head.php and then index.php

Solution

To get the desired output :

function getEvaluatedContent($include_files) {
    $content = file_get_contents($include_files);
    ob_start();
    eval("?>$content");
    $evaluatedContent = ob_get_contents();
    ob_end_clean();
    return $evaluatedContent;
}

$headin = getEvaluatedContent('head.php');

string = " <head> </head>";
$head = str_replace("<head>", "<head>". $headin, $head);
echo $head;

Output will be output string not file string :

 <head><title> Hello world </title> </head>