PHP Reading Lines from a Text File - php

Question

I am trying to search a line in a text file and then print the following three lines. For example, if the text file has
1413X
Peter
858-909-9999
123 Apple road
then my PHP file would take in an ID ("1413X") through a form, compare it to lines in the text file - essentially a mock database - and then echo the following three lines. Currently, it is echoing only the phone number (with the second half of the numbers wrong??). Thanks for your help.
<?php
include 'SearchAddrForm.html';
$file = fopen("addrbook.txt", "a+");
$status = false;
$data = '';
if (isset($_POST['UserID']))
{
$iD = $_POST['UserID'];
$contact = "";
rewind($file);
while(!feof($file))
{
if (fgets($file) == $iD)
{
$contact = fgets($file);
$contact += fgets($file);
$contact += fgets($file);
break;
}
}
echo $contact;
}
fclose($file);
?>

Answer 1

It is better to set some flag that you found id and some counter to count lines after it to achieve your aim.
<?php
include 'SearchAddrForm.html';
// $file = fopen("addrbook.txt", "a+");
$file = fopen("addrbook.txt", "r");
$status = false;
$data = '';
if (isset($_POST['UserID']))
{
$iD = $_POST['UserID'];
$contact = "";
rewind($file);
$found = false;
$count = 1;
while (($line = fgets($file)) !== FALSE)
{
if ($count == 3) // you read lines you needed after you found id
break;
if ($found == true)
{
$contact .= $line;
$count++
}
if (trim($line) == $iD)
{
$found = true;
$contact = $line;
}
}
echo $contact;
}
fclose($file);
?>
This kind of example how you can achieve this. And as you see in comment you should use $contact .= value, not $contact += value.
Also instead of reading you can take the whole file in array line by line using function file.
And why are opening file for writing?

Answer 2

What I did:
<?php
//input (string)
$file = "before\n1413X\nPeter\n858-909-9999\n123 Apple road\nafter";
//sorry for the name, couldn't find better
//we give 2 strings to the function: the text we search ($search) and the file ($string)
function returnNextThreeLines($search, $string) {
//didn't do any check to see if the variables are not empty, strings, etc
//turns the string into an array which contains each lines
$array = explode("\n", $string);
foreach ($array as $key => $value) {
//if the text of the line is the one we search
//and if the array contains 3 or more lines after the actual one
if($value == $search AND count($array) >= $key + 3) {
//we return an array containing the next 3 lines
return [
$array[$key + 1],
$array[$key + 2],
$array[$key + 3]
];
}
}
}
//we call the function and show its result
var_dump(returnNextThreeLines('1413X', $file));