How to use variable in the sed command using PHP to replace line
<p>I want to find and replace the whole line including adding new text in PHP using sed command in Linux. I tried below, but it does not work for variable but it works when I manually pass.</p>

<p>Example (This is Working): </p>

<pre><code>$var = exec("sed -i '/Tom/c Tom Rick' t1.conf"); 
</code></pre>

<p>Example (This is not working):</p>

<pre><code>$var1 = "Tom";
$var2 = "Rick";

$var = exec("sed -i '/$var1/c $var1 $var2' t1.conf");
</code></pre>

<p>I tried with double quote, but still no luck. Can someone please help me to resolve this problem.</p>