How to read fasta sequences from a file using PHP?

function read_fastas($filename){ 
    $fh = fopen($filename, 'r'); 
    $i= 0 ; 
    $sequences = array(); 
    while($line = fgets($fh)){ 
        $i++; 
        if($i%2==1){ 
            $sequence['header'] = $line; 
        } 
        else{ 
            $sequence['sequence'] = $line; 
            array_push($sequences, $sequence); 
        } 
    } 
    return $sequences; 
}