How to use array as query condition in php

In PHP development, it is often necessary to query data based on a set of conditions. This set of conditions is often passed to the program in the form of an array, and we need to convert it into query conditions in an SQL statement. This article will introduce how to use arrays as query conditions for querying.

1. Background

In actual development, we often need to query data in the database based on different conditions. These conditions may include simple relationships such as equal to, not equal to, greater than, less than, etc., or they may include complex logical relationships such as "or", "and", "not", etc. In order to facilitate the processing of these conditions, we usually encapsulate them into an array, for example:

$where = array(
    'id' => 1,
    'name' => 'Tom',
    'age' => array('gt', 18),
    'or' => array(
        'status' => 1,
        'score' => array('egt', 60)
    )
);

In the above code, the $where array represents a query condition, which includes id, name, age, status and score these five conditions. Their meanings are as follows:

• id=1
• name='Tom'
• age>18
• (status=1 or score> =60)

We need to convert this array into query conditions in SQL statements for executing database queries.

2. Implementation

In PHP, we can use string concatenation to convert arrays into query conditions for SQL statements. It should be noted that we need to determine the type of each array element and splice different conditions according to different types. The following is a simple implementation:

function whereToStr($where) {
    $str = '';
    foreach ($where as $k=>$v) {
        if (is_array($v)) {
            if ($k == 'or') {
                $str .= '(' . whereToStr($v) . ') OR';
            } elseif ($k == 'and') {
                $str .= '(' . whereToStr($v) . ') AND';
            } else {
                $str .= $k . ' ' . $v[0] . ' ' . $v[1] . ' AND ';
            }
        } else {
            $str .= $k . ' = "' . $v . '" AND ';
        }
    }
    return rtrim($str, ' AND');
}

This function will recursively traverse all elements in the array and generate corresponding query conditions based on the type of the element. If the element is a simple key-value pair, the corresponding equal condition is generated; if the element is an array, the "OR", "AND" operator, or conditional expression is generated based on the key name of the array.

According to the above implementation, we can convert the $where array into the following query conditions:

id = “1” AND name = “Tom” AND age > “18” AND (status = “1” OR score >= “60”)

3. Summary

Using arrays as query conditions to query is a PHP development process It is a relatively common requirement and a more convenient way. We can encapsulate the conditions into an array, and then convert the query conditions through simple string concatenation. In fact, some commonly used PHP frameworks have built-in similar query condition encapsulation and conversion functions, which can greatly simplify code writing.

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