While learning PHP online I am stopped at this eval function please help me. Why is there is a slash before $str2 in eval statement?
<?php
$string = "beautiful";
$time = "winter";
$str = 'This is a $string $time morning!';
echo $str. "<br>";
eval("\$str2 = \"$str\";");
echo $str2;
?>
The slash escapes the dollar sign, else in double quotes the dollar signs starts a variable name.
echo $var; // print the content of $var
echo "$var"; // print the content of $var
echo "\$var"; // print '$var'
echo '$var'; // print '$var'
Other thing is that you should find another book/tutorial for studying. Usign eval is unrecommended and in this case bad.
The last two lines of your code should be:
$str2 = $str;
echo $str2;
OR just
echo $str;
eval parses a string as php code, if you would remove them, both $str and $str2 would be replaced by their contents before it would get parsed by eval.
So with backslashes it would parse
$str2 = "This is a beautiful winter morning!";
Without the backslash it would parse
undefined = "This is a beautiful winter morning!";
Because it help identify that variable is used and variable with backslash are recognized by Compiler and then variable name is replaced with the value that it represents.
Backslash used to recognize PHP specials characters. In this case, \$str2 indicating a string contain "$str" not a variable named $str which is value 'This is a $string $time morning!'. So \$ while printed as string $ not as a variable.