PHP_FUNCTION(hello_world) {
    char *string;
    int  s_len;

    char *output_string = "You've entered: ";
    char *str;
    char newS[100];


    if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "s", &string, &s_len) == FAILURE) {
        RETURN_FALSE;
    }


    strcat(newS, output_string);
    if (s_len + strlen(newS) + 1 > sizeof(newS)) {
        RETURN_STRING("Your string is too long", 1);
    }

    strcat(newS, string);

//    str = estrdup(newS);
    RETURN_STRING(newS, 1);
}

/*
after compilation, when I execute
<?php
echo hello_world("Some string");
?>

the output is "lOYou've entered: some string" without the quotes. The left two bytes are different when the "Some String" is changed.
*/