Test code here: http://sandbox.onlinephpfunctions.com/code/8dc260415d49b04d2de53bf1f6efa625ee203bb2

pathinfo-alternative.php

<?php

$fileinfo = array(
    'dirname' => '',
    'basename' => '',
    'filename' => '',
    'extension' => ''
);

$path = '/a/b/c/abc.jpg';

$p = strrpos( $path, '/' );
$fileinfo['dirname'] = $p !== false ? substr( $path, 0, $p ) : '';
$fileinfo['basename'] = $p !== false ? substr( $path, $p + 1 ) : $path;
$p = strrpos( $fileinfo['basename'], '.' );
if ( $p !== false ) {
    $fileinfo['filename'] = substr( $fileinfo['basename'], 0, $p );
    $fileinfo['extension'] = substr( $fileinfo['basename'], $p + 1 );
} else {
    $fileinfo['filename'] = $fileinfo['basename'];
}

var_export( $fileinfo );

/* Output:
array (
  'dirname' => '/a/b/c',
  'basename' => 'abc.jpg',
  'filename' => 'abc',
  'extension' => 'jpg',
)
*/