The difference between PHP intval and int

The difference between PHP intval and int

$t = ' 165 ';

echo GetType ((int) ($t));
Echo ' Echo GetType (Intval ($t));

Output result: integer integer value:165

$t = ' a165 ';

echo GetType ((int) ($t));
Echo ' Echo GetType (Intval ($t));

Results Integer integer value:0,0

$string = "2a";
$string 1=intval ($string);
Echo ' $string value of 1: '. $string 1. ' Value of $string 2: ';//single quotation mark does not output variable, output as-is
$string 2= (int) ($string);
Echo $string 2