要了解一行PHP

Question

以下行是什么意思,特别是运营商.=？

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

在代码中

<?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);

?>

它似乎使某种类型的数组,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.

Answer 1

这是连接赋值运算符.它将连接或添加到字符串的末尾.所以:

$a = "Hi!";

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

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

在你的情况下

$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; */