PHP - Append only if match found in txt-file - php

Question

complete newbie to php here.
I have a simple application where I register different accesscodes. I've already written a function that checks the txt-file for duplicates, so that only new unique values are appended. This function works fine, see below.
function checkAccesscode($code)
{
$file=fopen ("files/codes.txt", 'r');
while ($string=fgets ($file))
{
if ($string!="")
{
$part=explode (";",$string);
$input=trim($part[0]);
if (stripos($input,$code)!==false)
{
return true;
}
}
else
{
return false;
}
}
}
Now, what I need is a similar, separate function which also checks for matches in a different txt-file (call it "codereg.txt"). Meaning that the code not only has to be unique, but it also has to be pre-registered in a different application/txt-file before it can be appended to its file.
Can anyone point me in the right direction?
Regards,
MadBer

Answer 1

Here's a function that reads the entire files into arrays and searches those with preg_grep().
<?php
define("UNIQ", "uniqueCodes.txt");
define("PREREQ", "preregCodes.txt");
function checkCodes(string $code):bool {
// Quote the search string to deal with regular expression special characters
$code = preg_quote($code,'/');
// Read the unique file. search with preg_grep(), return false if we get back a non-empty array
$uniq = file(UNIQ, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
if (preg_grep("/^{$code}/i", $uniq)) {
return false;
};
// Read the preregistered file and search with preg_grep(). Cast the result
// to a boolean and return. An empty array casts to FALSE, otherwise TRUE
$preq = file(PREREQ, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
return (bool)(preg_grep("/^{$code}/i", $preq));
}
$checks = ['abc123', 'abc124', 'abc126', 'abc200'];
foreach($checks as $check) {
echo "Checking code $check:".(checkCodes($check)?"pass":"fail")."<br>";
}
Unique Codes:
abc123;first code
abc124;second code
abc125; third code
Preregistered codes:
abc123: a
abc124: b
abc125: c
abc200: d
abc201: e
Results:
Checking code abc123:fail // non-unique code
Checking code abc124:fail // non-unique code
Checking code abc126:fail // unique, not pregistered
Checking code abc200:pass // unique, pre-registered