Discussion: The difference between a comma and a dot in PHP

With everyone to discuss, in PHP programming, the comma and dot difference of that point, there is a need for friends, may wish to refer to the next OH. In PHP, the comma is faster than the dot number, what is the reason for geometry? This article will be for everyone. Look at the code first: Learn the difference between a comma and a dot in PHP by example. Code: Echo ' 1+5= '. 1+5; Look at the above. The result of the output is 6. Not 1+5=6. It's kind of magical, isn't it? A magical example: Echo "1+5=". 5+1; Output 2 Replace position 5 and 1. The result becomes 2. Why is there no Exchange law in addition to PHP? Of course not. Let's not think about why. If I replace the dot above with a comma, try it. Echo ' 1+5= ', 5+1; Output 1+5=6echo ' 1+5= ', 1+5; Output 1+5=6 It can be seen that the expected results can be obtained only by using commas. So why not order the number? The comma is OK? Echo (' 1+5 '. 5) +1; Output 2 to the preceding parentheses. The result is the same. Prove that PHP is connected to the string before the addition calculation, according to the left-to-right direction. Since it is a string that is connected first. Then it should be "1+55". Then use this string to add 1. So why would it output 2? This is related to the mechanism of the string becoming a number in PHP. Take a look at the following example: echo (int) ' ABC1 '; Output 0 echo (int) ' 1ABC '; Output 1 echo (int) ' 2ABC '; Output 2 echo (int) ' 22ABC '; Output 22 As can be seen from the example above: if you cast a string into a number, PHP will search for the beginning of the string, if it starts with a number, if not, it returns 0. Back to the 1+55, since this string is 1+55, so the forced type conversion should be 1, on this basis add 1, of course 2. Verify that: Echo ' 5+1= '. 1+5; Output echo ' 5+1= '. 5+1; Output 6 echo ' 1+5= '. 1+5; Output 6 echo ' 1+5= '. 5+1; Output 2 proved to be correct. So why do you use commas without the above problem? The manual says. Comma is multiple Parameters. That is, multiple parameters, that is, a comma separated by the equivalent of n parameters. That is, ECHO is used as a function. This way, echo evaluates each parameter first, and then outputs it after the connection, so there is no problem with commas.

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