Source

File: wp-includes/pomo/streams.php

function readint32() {
			$bytes = $this->read( 4 );
			if ( 4 != $this->strlen( $bytes ) ) {
				return false;
			}
			$endian_letter = ( 'big' === $this->endian ) ? 'N' : 'V';
			$int           = unpack( $endian_letter, $bytes );
			return reset( $int );
		}