Show existing content of file when editing it PHP - php

Question

I open a .ini, then write some add some values to its parameters and then i saved it back.
My writing the content works perfectly fine, but when i open the file the previous content of that file is cleared.[Maybe due to my write mode].
What change should i do in my code to let user see what the previous content was when he edits a file.
file_get_contents($path.$filename);
/*Get All The datas from that file*/
$this->data['params'] = $this->parameter_m->get();
/*Getting the parameters to display on view*/
$this->data['parameters'] = parse_ini_file($path.$filename,true);
while (current($this->data['parameters']) )
{
$param_set = current($this->data['parameters']);
$param_type = key($this->data['parameters']);
foreach ($param_set as $key =>$value)
{
$this->data['parameters'][$param_type][$key] = $this->input->post($key);
}
next($this->data['parameters']);
}
$this->load->helper('file');
$this->load->library('ini');
$file = $path.$filename;
$ini = new INI($file);
$ini->read($file);
$ini->write($file, $this->data['parameters']);
My Write Function
function write($file = NULL, $data_file = array(), $sections = TRUE) {
$this->data_file = (!empty($data_file)) ? $data_file : $this->data_file;
$this->file = ($file) ? $file : $this->file;
$this->sections = $sections;
$content = NULL;
if ($this->sections) {
foreach ($this->data_file as $section => $data_file) {
$content .= '[' . $section . ']' . PHP_EOL;
foreach ($data_file as $key => $val) {
if (is_array($val)) {
foreach ($val as $v) {
$content .= $key . '[] = ' . (is_numeric($v) ? $v : $v ) . PHP_EOL;
}
} elseif (empty($val)) {
$content .= $key . ' = ' . PHP_EOL;
} else {
$content .= $key . ' = ' . (is_numeric($val) ? $val : $val ) . PHP_EOL;
}
}
$content .= PHP_EOL;
}
} else {
foreach ($this->data_file as $key => $val) {
if (is_array($val)) {
foreach ($val as $v) {
$content .= $key . '[] = ' . (is_numeric($v) ? $v : '"' . $v . '"') . PHP_EOL;
}
} elseif (empty($val)) {
$content .= $key . ' = ' . PHP_EOL;
} else {
$content .= $key . ' = ' . (is_numeric($val) ? $val : '"' . $val . '"') . PHP_EOL;
}
}
}
return (($handle = fopen($this->file, 'w+')) && fwrite($handle, trim($content)) && fclose($handle)) ? TRUE : FALSE;
}