假设这是静态字符串：
$name = "John";
$age = 37;
现在，假设用户在文本区域中输入以下值：
His name is {name}. His age is {age}
他也可以键入：
{name} is his name. {age} is his age.
现在，当用户提交表单时，PHP应该将这些字符串设置到特定的位置。
例如输出应该像：
His name is John. His age is 37
John is his name. 37 is his age.
好吧，由于您没有提供问题的具体细节，我只能推测您可能想要这个：
<?php
$name = "John";
$age = 37;
$userInput1 = "His name is {name}. His age is {age}";
$userInput2 = "{name} is his name. {age} is his age.";
$result1 = str_replace("{name}", $name, $userInput1);
$result1 = str_replace("{age}", $age, $result1);
$result2 = str_replace("{name}", $name, $userInput2);
$result2 = str_replace("{age}", $age, $result2);
echo "$result1<br>$result2";
这只是一个非常简单的文本替换。
根据您所说的，让用户从文本区域输入，然后将其传递给php并输出结果。这是一个演示：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<form action="a.php" method="post">
<textarea name="text_from_textarea"></textarea>
<button type="submit">Submit</button>
</form>
</body>
</html>
<?php
$name = "John";
$age = 37;
$userInput = $_POST["text_from_textarea"];
$result = str_replace("{name}", $name, $userInput);
$result = str_replace("{age}", $age, $result);
echo "$result";