了解一行PHP [英] To understand a line of PHP

问题描述

以下几行是什么意思，尤其是运算符.=?

What does the following line mean, particularly the operator .= ?

$query .= "UPDATE authors SET author=LOWER(author) WHERE id=2;";

在代码

<?php

$conn = pg_pconnect("dbname=publisher");

// these statements will be executed as one transaction

$query = "UPDATE authors SET author=UPPER(author) WHERE id=1;";
$query .= "UPDATE authors SET author=LOWER(author) WHERE id=2;";

pg_query($conn, $query);

?>

它似乎构成了某种数组，使得最后一个命令首先处理第一个查询，然后处理第二个查询.

It seems to make some sort of array such that the last command processes first the first query and then the second.

推荐答案

这是串联分配运算符.它将串联或添加到字符串的末尾.所以:

This is the concatenate assignment operator. It will concatenate or add to the end of the string. So:

$a = "Hi!";

$a .= " I";
$a .= " love";
$a .= " StackOverflow";
$a .= " a";
$a .= " lot";

echo $a; // echos "Hi! I love StackOverflow a lot"

以您的情况

$query = "UPDATE authors SET author=UPPER(author) WHERE id=1;";
$query .= "UPDATE authors SET author=LOWER(author) WHERE id=2;";
echo $query; 
/* echos "UPDATE authors SET author=UPPER(author) WHERE id=1; UPDATE authors SET author=LOWER(author) WHERE id=2; */

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