PHP reads the X line to Y line contents of a large file

It is necessary to read a few lines of a file, but the file is relatively large, so I studied the method of php to read a few lines of a large file and wrote a method, the code is as follows (with comments) :
If a cache file can be kept at 1 row, then reading the specified number of rows with the algorithm will be much faster than picking them all out.

 
$fp->seek($startLine - 1); 

In tests, this line of code reached the last line of 8MB text, with a memory footprint of 49KB, which was not bad, but 29KB with fgets skipping, which was still better.

 
function getFileLines($filename, $startLine = 1, $endLine = 50, $method = 'rb'){ 
$content = array(); 

if (version_compare(PHP_VERSION, '5.1.0', '>=')) { //  judge php Version (because it will be used SplFileObject . PHP>=5.1.0 )  
$count = $endLine - $startLine; 
$fp = new SplFileObject($filename, $method); 
$fp->seek($startLine - 1); //  Turn to the first N line , seek Method parameters from 0 Start counting  
for ($i = 0; $i <= $count; ++$i) { 
$content[] = $fp->current(); // current() Gets the current line content  
$fp->next(); //  Under the 1 line  
} 
} else { //PHP<5.1 
$fp = fopen($filename, $method); 
if (!$fp) 
return 'error:can not read file'; 
for ($i = 1; $i < $startLine; ++$i) { //  Skip the former $startLine line  
fgets($fp); 
} 

for ($i; $i <= $endLine; ++$i) { 
$content[] = fgets($fp); //  Read the contents of the file line  
} 
fclose($fp); 
} 
return array_filter($content); // array_filter Filtering: false,null,'' 
} 

Good results, SplFileObject class function is better.