PHP - Extract Custom Operators from String - php

Question

I have a MySQL database back-end which is searched via PHP. I'm trying to implement custom operators for detailed searching.
Here is an example:
$string = "o:draw t:spell card";
Where o: = Search by Description and t: = Card Typing. This would be similar to a custom syntax from a site like Scryfall https://scryfall.com/docs/syntax
Here is my work in progress example for o:
$string = "o:draw t:spell card";
if (strpos($string, 'o:') !== false) {
$text = explode('o:', $string, 2)[1];
echo $text;
}
The output is: draw t:spell card
I'm trying to get the output to respond with just: draw
However, it would also need to be able to accomplish this "smartly". It may not always be in a specific order and may show up alongside other operators.
Any suggestions on how to build around a system like this in PHP?
Example user searches:
Search Description + Type (new Syntax):
o:draw a card t:spell card
Search Card Name/Description (what it currently does):
Time Wizard
Search Card Name/Description (what it currently does):
Draw a Card
Combination of new and old syntax:
Time Wizard t:effect monster

Answer 1

I am unable to take your input all the way through to sql strings, because I don't know if you have more columns to access than the two that you have listed in your question.
To begin to script a parser for your users' input, you will need to understand all of the possible inputs that you wish to accommodate and assign specific handlers for each occurrence. This task has the ability to turn into a rabbit hole -- in other words, it may become an ever-extending and diverging task. My answer is only to get you started; I'm not in it for the long haul.
Declare a whitelist of commands that you intend to respect. In my snippet, this is $commands. The whitelist of strings with special meaning must not be confused with any card name strings -- I have added the best fringe case that I can find in the YuGiOh database (a card name containing a colon).
Build a regex pattern using the whitelist to find qualifying delimiting spaces in input strings.
Iterate the array generated by the regex-split input and assess each element to determine if/how it will be integrated into the WHERE clause of your sql.
At this early stage, it is fair to only allow one card name per input string, but certainly possible that users will wish to enter multiple card types to filter their expected result set.
I am electing to sanitize the user input by trimming leading and trailing whitespace and converting all letters to lowercase. I assume you will be running a modern database which will make case-insensitive comparisons.
Code: (Demo)
$tests = [
'o:draw a card t:spell card',
'Time Wizard',
'Draw a Card',
'Time Wizard t:effect monster',
'A-Team: Trap Disposal Unit',
't: effect o: draw a card atk: 1400 def: 600 l: 4 t: fairy',
];
$commands = [
'o' => '', // seems to be useless to me
't' => 'type', // card type
'atk' => 'attack', // card's attack value
'def' => 'defense', // card's defense value
'l' => 'level', // card's level value
];
$pattern = '~ *(?=(?:' . implode('|', array_keys($commands)) . '):)~'; // create regex pattern using commands lookup
foreach ($tests as $test) {
foreach (preg_split($pattern, strtolower(trim($test)), 0, PREG_SPLIT_NO_EMPTY) as $component) {
$colectomy = explode(':', $component, 2);
if (count($colectomy) < 2) {
if ($colectomy[0] !== 'draw a card') { // "draw a card" seems worthless to the query
$result[$test]['cardName (old syntax)'] = $component;
}
} elseif ($colectomy[0] !== 'o') { // o command seems worthless to the query
if (isset($commands[$colectomy[0]])) {
$result[$test][$commands[$colectomy[0]]][] = $colectomy[1]; // enable capturing of multiple values of same command
} else {
$result[$test]['cardName (new syntax)'] = $component;
}
}
}
}
var_export($result);
Output:
array (
'o:draw a card t:spell card' =>
array (
'type' =>
array (
0 => 'spell card',
),
),
'Time Wizard' =>
array (
'cardName (old syntax)' => 'time wizard',
),
'Time Wizard t:effect monster' =>
array (
'cardName (old syntax)' => 'time wizard',
'type' =>
array (
0 => 'effect monster',
),
),
'A-Team: Trap Disposal Unit' =>
array (
'cardName (new syntax)' => 'a-team: trap disposal unit',
),
't: effect o: draw a card atk: 1400 def: 600 l: 4 t: fairy' =>
array (
'type' =>
array (
0 => ' effect',
1 => ' fairy',
),
'attack' =>
array (
0 => ' 1400',
),
'defense' =>
array (
0 => ' 600',
),
'level' =>
array (
0 => ' 4',
),
),
)

Answer 2

You can so something like below to extract key value from string.
$tags = ['o:', 't:'];
$str = "t:spell card o:draw a card";
$dataList = [];
foreach($tags as $tag){
$tagDataLevel1 = explode($tag, $str, 2)[1];
$expNew = explode(':', $tagDataLevel1,2);
if(count($expNew)==2){
$tagData= strrev(explode(' ',strrev($expNew[0]),2)[1]);
}else{
$tagData = $tagDataLevel1;
}
$dataList[$tag] = $tagData;
//overwrite string
$str = str_replace($tag . $tagData,"",$str);
}
$oldKeyWord = $str;
var_dump ($dataList);
echo $oldKeyWord;