How can i set the type of a php-variable, which contains html-elements, as integer to use it in a if-statement?

I need to use a php-variable in a if-statement. The variable is defined with html-code that contains an id from a script.

$variable = "<label id='new_value'></label>";

If i call this variable, the result is always a number. Now I want to compare this variable in a if-statement with a normal number to call some other code. For example:

if($variable == 5){some code}

The problem is that my variable isn't a real number so I can't compare the html-element with a number like 5 in the if-statement, even if the variable would display the same number (5) when it's called on a website.

Is it possible to set the type from the variable as integer to compare it with another number in the if-statement or to define a new variable which extracts the content from the other variable and can be used as integer?

I hope someone can help me :-)