即使包含大写字母，也要比较2个字符串

I have a question about an if statement.

    if($_POST['billing_first_name'] == $tet['data']['0']['first_name']) {
    } 
    else 
    {
run code    
    } 

This code compares a string that it gets from a form with an already existing string.

It works. But when i dont add a capital letter, it runs the code after all.

So for example if i compare String with String it doesnt run the code (which is what i want) But when i compare string with String it runs the code (which i dont want) Only because theres no capital letter included at the beginning. Is there a way to fix this?

I solved it thanks to cmorrissey.

using strlower on both variables allows me to compare 2 strings no matter if there are capital letters inside one of the strings.

 if(strtolower($_POST['billing_first_name']) == strtolower($tet['data']['0']['first_name'])) {
    //do nothing
    }else {
    //run code
    }

Based on the comment the code is running fine it is an understanding of which block your are in.

if(condition){//code} will only run code when the condition is true ie

if("String" == "String"){echo "foo";} // will echo foo
if("string" == "String"){echo "foo";} // will not echo foo

In order to run code when false you add an else

// Will echo foo
if("String" == "String"){
    echo "foo";
} else {
    echo "bar";
}

// Will echo bar
if("string" == "String"){
    echo "foo";
} else {
    echo "bar";
}

A trick to getting ifs to execute when something is false is to use the ! (meaning not)

// Will echo bar
if("String" != "String"){
    echo "foo";
} else {
    echo "bar";
}

// Will echo foo
if("string" != "String"){
    echo "foo";
} else {
    echo "bar";
}