Detailed explanation of PDO::quote in PHP (with code examples)

When PHP connects to the database, it may be necessary to add quotation marks to the strings in the SQL statement. In order to solve this problem, we can use PHP's built-in functionsquote() function, this article will take you to take a look.

First let’s take a look at the syntax of the quote() function:

public PDO::quote    ( string $string   , int $parameter_type = PDO::PARAM_STR   ) : string

• $string: The string to which quotation marks are to be added.

• $parameter_type: Prompt the data type for the driver to choose the quotation mark style.

• Return value: Returns a quoted string, which can theoretically be safely used in SQL statements. If the driver does not support this method, false will be returned.

Code example:

1. Add quotation marks to ordinary strings

<?php
$servername = "localhost";
$username = "root";
$password = "root123456";
$dbname   = "my_database";
 
try {
    $pdo = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    echo "连接成功"."<br>"; 
    // $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $pdo->setAttribute(PDO::ATTR_CASE, PDO::CASE_UPPER);

    $string = &#39;Nice&#39;;
    print "Unquoted string: $string";
    echo "<br>";
    print "Quoted string: " . $pdo->quote($string) . "\n";
}catch(PDOException $e){
    echo $e->getMessage();
}

输出：连接成功
    Unquoted string: Nice
    Quoted string: 'Nice'

2 Dangerous strings in quotes

<?php
$servername = "localhost";
$username = "root";
$password = "root123456";
$dbname   = "my_database";
 
try {
    $pdo = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    echo "连接成功"."<br>"; 
    // $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $pdo->setAttribute(PDO::ATTR_CASE, PDO::CASE_UPPER);
    $string = &#39;Naughty \&#39; string&#39;;
    print "Unquoted string: $string";
    echo "<br>";
    print "Quoted string:" . $pdo->quote($string);
    }

输出：连接成功
Unquoted string: Naughty ' string
Quoted string:'Naughty \' string'

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